The present invention is a method to determine the cetane number of diesel fuels containing a fatty acid alkyl ester using multivariate fourier transform infrared models. In particular, the method determines the cetane number of diesel fuels containing rapeseed methyl ester.
The European Union is encouraging the use of rapeseed methyl ester (RSME) as a blending component of diesel fuel at levels up to 5% (from hereon known as biodiesel). The cetane number of such diesel fuels is measured in the laboratory by using an engine test method (ASTM D613). This method is not capable of measuring cetane number online, it is time consuming and requires a highly trained operator. As a result, a faster, repeatable method is needed to measure cetane number of biodiesel that could be used for process control and/or to certify the quality of products real-time, as they are being produced (i.e., online certification). Fourier Transform Infrared (FTIR) chemometric modeling can be employed to estimate the cetane number of diesel fuels online or in a laboratory. However, current FTIR methods involve chemometric models incapable of recognizing RSME-containing fuels, and, thus cannot be used for control of biodiesel production or certification.
Currently, an engine is used to measure cetane number of diesel fuels. The operation of the engine is carried out in a laboratory by a skilled operator. The engine analysis is time consuming, uses up a lot of fuel and it is not very repeatable (r=0.9 cetane number). An FTIR analyzer can be used as an alternative method to provide a direct measurement of cetane number online or in the laboratory. The FTIR analysis is fast and repeatable. However, the determination of cetane number of diesel fuels containing RSME by using chemometric data from Mid-FTIR spectroscopic analyzers has not been demonstrated. As a result, a method is needed to expand the use of FTIR spectroscopy to measure cetane number of diesel fuels with blended RSME.